Generally, when it is desired to exchange information securely with, for example, a portal server, a user-side communication terminal apparatus establishes an SSL (secure sockets layer) session. According to the SSL, a data encryption key is shared by a communication terminal apparatus and a server through key exchange done according to public key encryption and encrypted messages are exchanged. An example of such transactions is disclosed in U.S. Pat. No. 5,657,390. This protocol is also prescribed as RFC (request for comment) 4346 “The Transport Layer Security Protocol Version 1.1.”
Examples of the user-side communication terminal apparatus are image display apparatus such as digital broadcast receiving apparatus (TV receivers). A digital broadcast receiving apparatus establishes an SSL session with a portal server and, for example, displays an image that is delivered from the portal server.
In the above-described technique, in many cases, the server-side configuration is such that a portal server and a customer management server are provided separately. As a result, to provide a service that is unique to a customer or a terminal apparatus, it is necessary to authenticate the customer or the terminal apparatus through input of an ID, a password, or the like.